To support diagnosis of cardiac disease, three-dimensional data has been produced and displayed in which functional information about a cardiac muscle at respective positions in the cardiac muscle is three-dimensionally mapped. Such three-dimensional data is produced using volume data obtained by imaging the heart of a patient by a medical diagnostic imaging apparatus.
In addition, polar maps have been produced and displayed. The polar map can express all of the functional information included in the three-dimensional data in a single image. The polar map, which is also called a “bull's eye plot”, is an image in which the three-dimensional data is developed on a plane. Specifically, the polar map is an image in which three-dimensional data of the functional information at each of a plurality of short-axis cross sections from a cardiac base to a cardiac apex is projected on a “circle the center of which corresponds to the cardiac apex and the periphery of which corresponds to the cardiac base”.
For example, the three-dimensional data is a three-dimensional contrast enhanced image of the heart imaged in a late phase. The three-dimensional contrast enhanced image of the heart in the late phase is data indicating a survival rate of cardiac muscle cells because contrast media are accumulated in necrotic or ischemic cardiac muscle cells. Another example of the three-dimensional data is a three-dimensional perfusion image in which “index values indicating perfusion dynamics of blood in the cardiac muscle” calculated from time series data of the three-dimensional contrast enhanced image are mapped. The three-dimensional perfusion image is also data indicating the survival rate of the cardiac muscle cells.
In the diagnosis of cardiac disease, it is important to grasp a positional relation between the cardiac muscle and coronary arteries that nourish the cardiac muscle. The coronary arteries are arteries that supply bloodstream (oxygen) to the cardiac muscle. No blood is supplied from a portion where the coronary arteries are constricted or completely obstructed to the downstream cardiac muscle. As a result, a motion function of a heart wall deteriorates. A doctor thus needs to grasp the portion of the cardiac muscle where the motion function deteriorates and further the portion of the coronary artery dominating the portion of the cardiac muscle.
An apparatus has been developed that has a function to extract the coronary arteries from the three-dimensional contrast enhanced image in the artery phase by segmentation processing, produce and display a rendering image after performing rendering processing on the extracted coronary arteries, and produce and display a polar map from the three-dimensional shape of the extracted coronary arteries. A technique has been also proposed in which a polar map is produced and displayed in which a “three-dimensional contrast enhanced image in the late phase” and a “three-dimensional shape of the coronary arteries”, which are obtained from a magnetic resonance imaging (MRI) apparatus, are developed on the same plane.
Recently, an apparatus has been developed that calculates wall motion information (e.g., strain and displacement) at respective positions in the cardiac muscle by speckle tracking using the time series data of the three-dimensional ultrasound image. The apparatus can produce a three-dimensional analysis image (also called “plastic bag”) in which the calculated wall motion information is mapped on a surface rendering image of the cardiac muscle in colors in accordance with the values, and further can produce a polar map from the three-dimensional analysis image. The wall motion information obtained by echocardiography makes it possible to quantitatively analyze motion functions in respective regions of the cardiac muscle and to perform a diagnosis on heart function in more detail by comparing with the three-dimensional data indicating the survival rate of the cardiac muscle cells.
Conventionally, a doctor checks the constricted portion in the coronary arteries with reference to the rendering image or the polar map of the coronary arteries obtained by a contrast enhanced CT inspection and also checks the portion of the cardiac muscle where the motion function deteriorates from the polar map of the wall motion information obtained by the echocardiography. In this way, in the conventional technique, a doctor observes two images separately, and grasps a positional relation between the portion of the cardiac muscle where the motion function deteriorates and the constricted portion of the coronary artery.